ABSTRACT
Towards the end of a career that spanned almost 60 years, Ivan Petrovich Pavlov, eminent Russian physiologist, member of the Royal Society and Nobel prize-winner, concluded that sleep was a relatively straightforward process characterised by 'spreading cortical inhibition'. By this Pavlov meant that as brain cells fatigue, they switch off one by one. By the early 1930s considerable information had been accumulated concerning biological events during sleep, the periodicity or time schedule of sleep, and also the physiological and psychological consequences of sleep deprivation. Electroencephalogram (EEG) appeared to provide a method capable of measuring the onset, progress, and depth of sleep. In 1968 internationally agreed criteria for interpreting the 'polysomnogram' were published. These criteria, incorporating the accumulated wisdom of 40 years of brain-wave recording, remain in use today, and describe five 'stages' of sleep. Assessed in terms of the number of experiments reported in scientific journals, interest in sleep research and in the application of EEG-related measurement techniques.
